11 attacks by the 'Blaster' worm - success would have rendered the machine unusable

3 attacks by the 'Slammer' worm - success would have left machine crippled and prone to crashing

36 fake security announcements/adverts for fake security software posing as warnings. Reacting to these could leave a PC clogged with spyware.

Over the course of the whole experiment, on average at least one attack an hour came from a dangerous computer bug with the ability to cripple an unprotected PC. And at least one attack per night was even more serious - an attempt to hijack the computer entirely – which could lead to the computer being turned into a 'zombie PC' and used to carry out criminal activity without the owner's knowledge.

The experiment demonstrates the vulnerability of unprotected home PCs to malicious hackers.

According to Symantec, 86 per cent of all targeted attacks on computers are aimed at home users. There are an estimated 200,000 malicious programs in existence.

Starting today, the BBC News Website is running a whole week of special features looking at the issue of hi-tech crime and giving people advice on they can stay safe online.

As part of the BBC News Website's 'Cracking Hi-Tech Crime[ specials the BBC also talks to the hi-tech criminals behind the viruses, 'phishing' e-mails and malicious programs putting home PCs at risk.

One hacker the BBC spoke to claims to have earned $10,000 a day from computer crime, another says that they can hack into many online shops within 3-4 hours and sell the data on for anything between $100-500. Unconcerned about the risk of arrest the hacker adds: "How can a cop catch me? Catch me if they can!"